Efficient Luminaire with Directional Side-Light Extraction

ABSTRACT

Luminaire with directional side-light extraction comprises a light pipe with a light-carrying core, and with a light-extraction structure along a first longitudinal side of the luminaire, confined to a radial swath of the luminaire, along the longitudinal axis of the luminaire, of substantially less than 180°. The second end has light-saving structure for directing saved light from the second end towards the first end, at redirection angles other than an excluded range of redirection angles, so long as the photon content of light at so-called alpha redirection angles is at least 10 percent of the photon content of light at so-called beta redirection angles, where the excluded range of redirection angles is defined by a mathematical formula. The light-extraction means is adjustable to accommodate angular distributions of light from various light sources.

This application is a continuation-in-part of application Ser. No.11/108,279 filed on Apr. 18, 2005.

FIELD OF THE INVENTION

The present invention relates to luminaires comprising light pipes inwhich light is extracted from the side of the light pipe in apreferential direction. More particularly, the invention relates toextraction of light from the side of light pipes in an efficient, andpreferably, uniform manner while accommodating the angular distributionof light from different light sources.

BACKGROUND OF THE INVENTION

Light pipes are primarily used for lighting in two main modes. In anend-light mode, the light pipe is optimized to carry light along itslength, and transmit it to the output face of the light pipe, typicallyto a lighting fixture. In a side-light mode, light is extracted from theside of the light pipe and provides illumination along its length. Thepresent invention relates to a side-light mode in which light isextracted in an efficient, and preferably uniform, manner from the sideof a light pipe. The portion of a light pipe in which light is extractedfrom the side of the light pipe is referred to herein as a “luminaire.”Luminaires can be integrated with end-light mode light pipe systems orluminaires can be directly coupled to a source.

One known luminaire is disclosed in U.S. Pat. No. 5,857,761 to Abe etal. The Abe et al. patent is directed to the specialized application ofproviding light to a thin, flat display panel such as used as a displayfor notebook computers. Abe et al. had a lesser need for efficiency anddirectionality of light extraction from a luminaire as compared toapplications for lighting wide areas, as, for instance, a person'soffice. Abe et al., in fact, employs diffusion members in someembodiments to achieve uniformity at the expense of efficiency anddirectionality since their luminaire does not achieve on its ownadequate uniformity.

U.S. Pat. No. 6,488,397 to Masutani et al. discloses a luminaire with aconstant-width strip of light-extraction means. However, the Masutani etal. disclosure does not address the concerns of efficiency anduniformity of illumination addressed by the various embodiments of thepresent invention.

US Patent Publication No. 20020159741A1 discloses various applicationsof luminaires. However, such applications do not address the efficiencyand uniformity of illumination addressed by the various embodiments ofthe present invention.

In connection with an embodiment of the invention including a reflectingenclosure spaced from a luminaire, U.S. Pat. No. 6,095,673 to Goto etal. discloses a luminaire with an enclosure. However, the enclosure ofGoto et al. intimately contacts the luminaire so that there is no airgap between luminaire and enclosure.

It would be, thus, desirable to provide luminaires having embodimentsproviding efficiency of illumination, and preferably also uniformity ofillumination arranged, while accommodating the angular distribution oflight from different light sources.

SUMMARY OF THE INVENTION

The present invention provides, in a preferred form, a luminaire withdirectional side-light extraction. The luminaire comprises a light pipewith a light-carrying core. The light-pipe has a first end in whichlight from a first light source is received, a second end, and alongitudinal axis. The surface of the core of the light pipe has alight-extraction means along a first longitudinal side of the luminaire,which is confined to a radial swath of the luminaire, along thelongitudinal axis of the luminaire, of substantially less than 180°.Angles passing through a first plane intersecting a radial center of thelight-extraction means are termed alpha angles or alpha componentangles; and angles passing through a second plane orthogonal to thefirst plane are termed beta angles or beta component angles. Alphaangles are referenced to the second plane and beta angles beingreferenced to the first plane. Light-saving means are included on thesecond end for directing saved light from the second end towards thefirst end, at redirection angles other than an excluded range ofredirection angles, so long as the photon content of light at alpharedirection angles is at least 10 percent of the photon content of lightat beta redirection angles. The excluded range of redirection angles isdefined by:|β_(r)|<=20° and |α_(r)|<|β_(r)|/10,

where β_(r) is the beta redirection angle and α_(r) is the alpharedirection angle.

In one embodiment, the light-extraction means is adjustable toaccommodate angular distributions of light from each one of the lightsources of a metal halide lamp, an LED lamp or a halogen lamp, one at atime.

In another embodiment, the light-extraction means is adjustable toaccommodate angular distributions of light from a high illuminance lightsource with luminance greater than 100,000 Nit.

In yet another embodiment, the light-extraction means is adjustable toaccommodate angular distributions of light from an array of LED lamps,which lamps may have different colors.

Preferably, the light-saving means redirects saved light at alpha andbeta redirection angles defined by the equation:20<√{square root over (α_(r) ²+β_(r) ²)}<60,

where β_(r) is the beta redirection angle and α_(r) is the alpharedirection angle.

The foregoing inventive luminaires achieve a high efficiency, largelydue to inclusion of light-saving means at the second end of theluminaire. Various embodiments of the invention also achieve a highdegree of uniformity of illumination. This is true, although theinclusion of the light-saving means often requires a more carefulpatterning of the light-extraction means to achieve uniformity.

Other features and advantages of the invention will become apparent fromthe following specification in connection with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, schematic side view of a sidelight illuminationsystem according to the present invention.

FIG. 2A is an isometric view of a section of luminaire 20 of FIG. 1,with a stippled region comprising light-extraction means; and FIG. 2B isa simplified cross-sectional view of the luminaire of FIG. 2A.

FIG. 3 are side views of three different luminaires, together with athree-axis legend, and with stippled regions comprising light-extractionmeans.

FIG. 4 is a side view of luminaire 40 a shown in FIG. 3.

FIGS. 5 and 6 are plots of alpha redirection angles versus betaredirection angles.

FIG. 7A is an end view of a luminaire and a target region to beilluminated.

FIG. 7B is a side view of the structures of FIG. 7A.

FIG. 8A is an end view of a pair of luminaires and a target region to beilluminated.

FIG. 8B is a side view of the structures of FIG. 8A.

FIG. 9 is a side view of a luminaire having a roughened surface at itssecond end.

FIG. 10 is a graph of optical properties of the roughened surface shownin FIG. 9.

FIG. 11 is a side view of a pair of integrally joined luminaires.

FIGS. 12 and 13 are cross-sectional views of luminaires.

FIG. 14A is a plot of light-extraction efficiency versus length along aluminaire for different tilt angles of a mirror serving as alight-saving means.

FIG. 14B is a plot showing the intensity distribution for the lightsource used to generate the data of FIG. 14A.

FIG. 15A shows two sections of a single light pipe with a luminairesection light-extraction means in a varying pattern of light-extractionefficiency.

FIG. 15B is a plot showing relative efficiency versus end tilt angle ofa mirror.

FIG. 15C is a plot of relative efficiency of light-extraction meansversus length of a luminaire for different radial swaths oflight-extraction means.

FIGS. 16A and 16B show cross-sectional views of luminaires with anundesired reflector and a desired reflector, respectively.

FIG. 17 is a textured pattern of light-scattering means.

FIG. 18 is a cross-sectional view of a small section of the surface of aluminaire, greatly magnified, showing a textured pattern.

FIGS. 19A-19D show alternative shapes that can replace the hemisphericalshapes of FIG. 18.

FIG. 20 is a sectional view of a light pipe with light-extraction meanscomprising two modalities.

FIG. 21 is a block diagram of a light source comprising severalcomponent parts.

FIG. 22A is a perspective view of a preferred embodiment of the lightsource of FIG. 21; and FIG. 22B is a front end view of that embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a sidelight illumination system 10 showing the principle ofextracting light from the side of a light pipe. System 10 includes alight source 12, a light pipe 14, and a target surface 16 to beilluminated. Arrows 18 show directional illumination of target surface16 from a region 20 of fight pipe 14 that emits light from the side ofthe light pipe. Side-light emitting region 20 is referred to herein as a“luminaire.” Section 20 may comprise either a fraction of the length oflight pipe 14 that is optimized to provide side light extraction, withsome or all of the remaining section(s) (e.g., region 21) of the lightpipe 14 optimized to transmit light along the longitudinal axis of thelight pipe.

In one preferred embodiment, light source 12 is placed outside of acontainer represented by phantom-line box 13. Container 13 may be anenclosed or open refrigerated container. For instance, container 13 maybe an enclosed freezer case for displaying food or other items.

FIG. 2A shows a light ray 24 entering a core 26 of luminaire 20 ofFIG. 1. Light rays 28 pass in a preferential direction from the side ofluminaire 20, due to the presence of light-extraction means 30, shown asa strip on luminaire 20. Light-extraction means 30 are shown stippledfor convenience of illustration. The direction of light rays 28 can bemore easily observed in FIG. 2B. As shown, light-extraction means 30 areconfined to a radial swath 32 about the longitudinal axis of theluminaire, such radial swatch preferably being substantially less than180°. Light ray 34 exits the end of luminaire 20, and representsresidual light that has not exited the luminaire via thelight-extraction means. It may be desirable to capture light ray 34, andredirect it back through luminaire 20.

FIG. 3 shows one way to capture and redirect light rays such as lightray 34 in FIG. 2A. As shown in FIG. 3, one way to capture light ray 34is with a mirror, such as shown on luminaires 40 a, 40 b and 40 c inFIG. 3 as mirrors 42 a, 42 b and 42 c, respectively. These mirrors mayhave specular reflecting surfaces, if desired, The angles made bymirrors 42 a-42 c with respect to the respective light-extraction means44 a, 44 b and 44 c significantly affects how light redirected back intothe luminaires behaves optically. Accordingly, legend 46 shows mutuallyorthogonal X, Y and Z planes, corresponding to the X-Z axes shown inlegends 48 a and 48 b on the left-shown ends of luminaires 40 a and 40b. Similarly, legend 46 corresponds to the Y-Z axes shown in legend 48c, on the left of luminaire 40 c.

Legend 46 shows alpha (α) and beta (β) angles. Textual notations to theleft of luminaires 40 a-40 c show, from top to bottom, mirrors 42 a and42 b angled at plus (+) and minus (−) alpha angles, and mirror 42 cangled at a plus (+) beta angle. With reference to FIG. 3, anglespassing through a first plane (not shown) intersecting a radial centerof the light-extraction means are termed alpha angles or alpha componentangles; and angles passing through a second plane (not shown) orthogonalto the first plane are termed beta angles or beta component angles.Alpha angles are referenced to the second plane and beta angles beingreferenced to the first plane.

FIG. 4 clarifies the term “redirection” angle as used herein. In FIG. 4,showing luminaire 40 a, angle 50 is the angle of light redirected bymirror 42 a for an on-axis ray where the mirror is a specular mirror.Angle 50 is thus termed a “redirection” angle. Angle 52, in contrast, istermed a “tilt” angle, which is the angle made by the mirror withrespect to the Y axis as shown in legend 48 a. For a specular mirror 42a, the redirection angle is twice the tilt angle.

A flat mirror at the end of the luminaire is an example of a lightsaving means where the redirection angle is 0. With a flat mirror, thereis a high probability of coupling light from the input end of theluminaire to the output end of the luminaire and then back the whole wayto the input end. This flux can result in a loss of luminaire efficiencyif that light couples back into the transport fiber 21 and/or the lightsource 12 of FIG. 1.

Preferred Redirection Angles

The mirrors shown in FIGS. 3 and 4 serve as one type of light-savingmeans; that is, means for saving what otherwise would be wasted light(e.g., ray 34, FIG. 2A). Preferred redirection angles are shown in FIG.5, which is a plot of alpha redirection angles versus beta redirectionangles. The preferred angles comprise a doughnut-shaped area 60, showncross-hatched, defined by the equation:20<√{square root over (α_(r) ²+β_(r) ²)}<60,

where β_(r) is the beta redirection angle and α_(r) is the alpharedirection angle.

Two triangular shaped regions 62 are excluded from the preferredredirection angles. These regions 62 are defined by the equation:|β_(r)|<=20° and |α_(r)|<|β_(r)|/10.Regions 62 represent the βphd r from −20 to +20° (i.e., β from −10 to10) taught by U.S. Pat. No. 5,857,761 to Abe et al. at Column 4, Lines46-56, for instance, in which the alpha angles are zero, plus atolerance band of alpha angles which increase at increasing beta angles.The Abe et al. patent states that (beta) mirror tilt angles greater than10 degrees—according to the geometry defined in present FIG. 3—areunsuitable since it produces illumination “uneven along the radiationmember,” Col. 4, Lines 52-56. The other angles within the circularregion 64, other than the foregoing excluded angles, are also preferred.Such angles are defined by:0<√{square root over (α_(r) ²+β_(r) ²)}<20apart from the foregoing, excluded angles.

FIG. 6 shows other preferred and excluded redirection angles. It issimilar to FIG. 5, but the excluded area 63 comprises a rectangledefined by: β_(r) from −20 to +20°, and α_(r) from −2° to +2°. This areais excluded to distinguish over the −10 to +10 beta angles of the citedAbe et al. patent, with a different alpha tolerance band used. Thetolerance allowed is plus or minus 1° alpha. Area 60, as in FIG. 5,shows preferred angles. Area 65 also shows preferred angles, andexcludes rectangular area 63.

A particularly preferred range of redirection angles is from −20 to −30(and most preferably −25) alpha redirection angles, with betaredirection angles being negligible.

In addition to the preferred ranges of alpha and beta redirection anglesdescribed above, to further distinguish over the cited patent to Abe etal., the condition is preferred that the photon content of light atalpha redirection angles is a substantial percentage of the photoncontent of light at beta redirection angles. That percentage ispreferably 10, although it could also be 20, 30 or 40.

Applications

One application for luminaires of the present invention is shown inFIGS. 7A and 7B. In these figures, a luminaire 66 havinglight-scattering means 67 directs light at an angle 68 to a targetregion 69. The radial swath 67 of light-extraction means is related tothe size of the illumination pattern perpendicular to the long axis ofthe luminaire. In general, narrow radial swaths produce narrowillumination patterns and wide radial swaths produce wide illuminationpatterns. The radial swath of light-extraction means may preferably befrom 60 to 130° for a luminaire 6 feet away from a target region to beilluminated. Where a luminaire is 20 feet above a larger-sized targetregion to be illuminated, a preferred radial swath may be from 20 to90°. Given the shape of the light pipe used in the luminaires a personof ordinary skill in the art will find it routine to select anappropriate radial swath based on the region to be illuminated and thedistance from a luminaire (or luminaires), based on the presentspecification. The cross sectional shape of the luminaire is preferablyround but could be shaped so as to provide further control over theillumination distribution produced by the luminaire. Secondary optics,such as lens arrays, cylindrical lens, and Fresnel lenses can becombined with the side lighting light pipe.

For increasing efficiency of lighting by a luminaire with a 90° swathwidth, it is desired that the ratio of luminaire length to the maximumcross-sectional dimension of the luminaire exceed 20, and preferablyexceeds 30. This helps to ensure that a high fraction of the lightentering the luminaire will strike the extraction pattern and therebyprovide high efficiency.

Another application for luminaires of the invention is shown in FIG. 8Aas a plurality of luminaires, for instance, 70 a and 70 b, havingrespective light-scattering means 71 a and 71 b for directing lighttowards a target region 74. Angles 72 a and 72 b are preferably in therange from 20 to 60°. However, the light is not strictly confined towithin angles 72 a and 72 b. Luminaires 70 a and 72 a cooperate witheach other by both providing light in area 76 of region 74, so that thetarget region 74 is more uniformly illuminated. However, more than twoluminaires can be used in this application, if desired.

FIG. 8B shows a side view of the luminaires 70 a and 70 b and targetregion 74. Region 74 may be food in a in a cooler or freezer case in agrocery store, for instance. Luminaires 70 a and 70 b provide lightingfor the food, in energy efficient but, more importantly, a lowmaintenance manner compared to conventional fluorescent lighting, forinstance. There are two areas where maintenance is reduced whenreplacing fluorescent tubes in cooler or freezer case with the presentluminaire.

The low temperature environment is one area. Fluorescent lights do notperform well in low temperature environments. In cooler cases, allfluorescent bulbs are surrounded by a protective, air-tight coveringthat seals out the cold and provides some self-heating from the bulbitself. The heat is needed to keep the mercury in vapor phase in thetube. If the seal is broken, heat escapes and the bulb generatessignificantly less light. Any time the bulb is changed or the fixture isphysically shaken, there is a risk that the seal could be broken. Toreplace or repair the seal, the contents of the case would most likelyneed to be removed. Beneficially, the present luminaire does not havethe same constraints; it will function the same way inside a cooler orfreezer case or outside. No seals are required to sustain a workabletemperature environment in the cooler case.

Tube breakage is the second area in which the present luminaire resultsin less maintenance. There is a significant risk of bulb breakage whenfluorescent tubes are replaced in cooler or freezer cases. Because ofthat risk, such cases are typically emptied of food before the bulb isreplaced. This reduces the risk of glass and mercury contamination ofthe food stuff. This is a costly, time-consuming operation that will beeliminated with the use of the present luminaire, since no glass ormercury is used. In the event that a tube does break in the cooler orfreezer case, the goods become contaminated with glass and are presumedcontaminated with mercury and so must be discarded. This is costly aswell.

The present luminaires do not need to be replaced except in the rarecase where one becomes broken. The light source for the presentluminaires are outside of the cooler or freezer case and can easily bereplaced without shutting down and emptying the case and without theneed of entering the case.

As one example of an application of FIGS. 8A and 8B, with target regions76 being 2.5 feet wide, luminaires 70 a and 70 b are set in from eitherside by one inch (see FIG. 8B). Target region 76 is 6 inches from thecenters of the luminaires (see FIG. 8A). Each luminaire has a 12 mmdiameter. Typically, each luminaire has a radial swath significantlyless than 90°. This makes the angular distribution of the light in theacross-luminaire direction reasonably narrow. As will be apparent fromFIG. 8A, the luminaires can then be aimed via rotating them about theirrespective optical axes. The illuminance distribution is then asuperposition of the patterns generated by each of the two individualluminaires, and can be designed so as to be uniform.

The generally parallel arrangement of luminaires of FIGS. 8A and 8B maybe used in other applications, as will be apparent to those of ordinaryskill in the art. For instance, it may be used in a jewelry or museumdisplay case, by way of example.

Further Light-Saving Means

In addition to the use of flat specular mirrors for light-saving meansdescribed above (e.g., 42 a, FIG. 3), a redirection means, whichredirects the light over a range of angles, may be used, as described inFIGS. 9 and 10. In FIG. 9, a luminaire 80 with light-extraction means 82includes a nominally flat but roughened surface 84 according to thegeometry indicated by Y-Z axes legend 86. Roughened surface 84, locatedat the “second” end of the luminaire (as used herein), can be adjustedto redirect light over a range of angles with more directionality than adiffuse reflector but less directionality than a specular mirror. Analternative embodiment that redirects light over a range of angles wouldbe a holographic diffuser combined with a specular mirror. Yet anotherembodiment would be to stipple the end face of the luminaire and thenuse a specular mirror.

Although there are many redirection distributions that a non-specularend surface can produce, a Gaussian scatter distribution is a typicalshape. A Gaussian redirection distribution can be described according tothe following equations:${{Redirection}\quad\left( {\alpha_{r},\beta_{r\quad}} \right)} = {P_{o}{\exp\left( {{- \frac{1}{2}}\left( \frac{\alpha_{r}^{2} + \beta_{r}^{2}}{\sigma^{2}} \right)} \right)}}$where σ is a parameter that controls the width of the scatterdistrubituion and P₀ is a constant for a given value of σ and totalreflectivity. σ of about 15° provides a reasonable compromise between adiffuse reflector that redirects light to angles that are too large anda specular mirror with a 0° tilt that does not provide sufficientredirection of the light.

FIG. 10 depicts the reflected scatter distribution when a ray hits theend mirror at and off-axis angle.

Another form of light-saving means can be formed as shown in FIG. 11.FIG. 11 shows a pair of luminaires 100 a, 100 b, each having arespective light source 102 a, 102 b, at its “first” end (as usedherein). Luminaire 102 a has light-extraction means 104 a, and luminaire100 b has light-extraction means 104 b. A light-saving means 106constitutes a bend region at the respective second ends of the pair ofluminaires 100 a, 100 b. Thus, light from light source 102 a that doesnot exit luminaire 100 a via light-extraction means 104 a is“redirected” into luminaire 100 b as saved light. This avoids wastinglight.

Miscellaneous

Regarding preferred constructions of luminaires, FIG. 12 shows aluminaire 110 having a core 112. FIG. 13 shows a contrasting luminaire114 having a core 116 and also a transport cladding 118. Luminaire 110of FIG. 12 relies on a “cladding” consisting of air. Typically,transport cladding 118 of FIG. 13 will have an index of refractionsubstantially larger than that of air but substantially less than thatof the core. Luminaire 110 of FIG. 12 is free of such a transportcladding. The use of a non-absorbing transport cladding as in FIG. 13can typically result in about one percent efficiency increase over theuse of an air cladding as in FIG. 12.

Preferably, the core of each of the luminaires of FIGS. 12 and 13comprises an acrylic polymer or quartz. The core material will be chosenfrom material that possesses a low coefficient of light absorption tomaximize the light throughput of the material, so as to maximizeefficiency. High quality optical grade quartz is very efficient, with alow light absorption coefficient. However, this material is easilybroken. It has been found that some acrylic polymer materials also havelow light absorption coefficients and make highly efficient luminairedevices. Such materials will be apparent to those of ordinary skill inthe art.

Uniformity of Illumination—Patterning Light-Extraction Means

A concern arises with increasing the efficiency of illumination byincorporating light-saving means in luminaires. Increasing theefficiency often makes it more difficult to achieve uniformity ofillumination. Typically, the present invention will achieve highuniformity of illumination, for instance, with illuminance over each ofeach sequential 5 percent length of a luminaire being uniform to within10 percent of the average illuminance along the length of the luminaire.The present invention can achieve high uniformity by carefullycontrolling the profile of light-extraction efficiency oflight-extraction means along the length of a luminaire.

FIG. 14A plots light-extraction efficiency versus alpha tilt angles of amirror at the second end of a luminaire (e.g., mirror 42 a, FIG. 3), forachieving high uniformity of light for a 610 mm-long, round luminairewith a 19 mm diameter and an 85-° radial swath width. The flux enteringthe luminaire is coupled from a light source (not shown) to theluminaire using a cladded transport fiber. The light source has anintensity distribution 128 as shown the plot of FIG. 14B. As apparentfrom the above description, the tilt angle of a mirror results in atwice-as-large angle of light “redirected” by the mirror. The extractionefficiency curves of FIG. 14A for achieving high uniformity of light arenow explained in more detail.

As shown in FIG. 14A, for an alpha tilt angle of −15, curve 120 showsthat the efficiency will have a non-monotonic pattern, with theextraction efficiency 122 at the end of a luminaire being less thanmaximum. For a tilt angle of 0° alpha, curve 124 shows that theefficiency of light extraction need only increase substantiallymonotonically to a peak at 122 (second end of luminaire). For a tiltangle of +15° alpha, curve 126 shows that the light-extractionefficiency increases non-monotonically, with such efficiency reaching apeak at 122 (second end of a luminaire).

A preferred way of arriving at a profile for light-extraction efficiencyalong the length of a luminaire is to use an iterative design approach,testing each iterative design with appropriate light-modeling software.This approach is described in a paper by W. J. Cassarly and B. Irving,“Noise tolerant illumination optimization applied to display devices,”Proc. SPIE, Vol. 5638, Pages 67-80, February 2005. This paper describesan iterative approach to adjusting the extraction pattern so as toachieve a desired spatial illumination distribution. The illuminationoutput distribution for a starting extraction pattern is used to reducethe extraction where the illumination output is too high and increasethe extraction where the illumination output is too low. Onceadjustments to the extraction pattern are made, the illumination outputis recomputed and a new extraction pattern is estimated. This procedureis repeated iteratively. After a number of iterations, the extractionpattern required to achieve the specified spatial illuminationdistribution is obtained. One example commercial software package thatcan be used to compute the illumination output distribution isLightTools® software by Optical Research Associates of Pasadena, Calif.

One particular pattern of light-extraction means is shown in FIG. 15A.FIG. 15A shows two sections of a luminaire 130 with a pattern oflight-extraction means 132. For illustration of the variation inextraction density along the length of the luminaire, light-extractionmeans 132 are shown as rectangular stripes orthogonal to the length ofthe luminaire. Means 132 could be a suitable paint containinglight-extraction particles, as explained below, by way of example, Thedominant factor when using paint is the density of the paint pattern,not the shape of each painted region. This means that circular, oval,rectangular, or any other shape that can be applied in a controlledmanner can be used.

In FIG. 15A, light-extraction means 132 are divided into twenty sections132 a, 132 b, etc. Phantom lines 136 and 138 mark the beginning and endof section 132 a of the light-extraction means. Each section (e.g., 132a) of the light-extraction means has the same light-extractionefficiency along its length. It is preferred for uniformity of lightillumination that the gaps (e.g., 133) in the light-extraction meansalong the length of the luminaire are less than about 20 percent of thediameter of the light pipe. Much smaller gaps are used when it isdesired to minimize the structure observed when looking back into theluminaire. The pattern of light-extraction means of FIG. 15A correlatesmostly with curve 124 of FIG. 14A.

Preferably, a pattern of light-extraction means such as shown in FIG.15A achieves uniformity of light extraction such that the followingrelation applies: average Illuminance over each of each sequential 5percent length of the luminaire—given that twenty sections might beused—is uniform to within 10 percent of the average illuminance alongthe length of the luminaire.

FIG. 15B shows light extraction efficiency as a function of the alphacut tilt angle of a flat mirror. Curves 136 a, 136 b and 136 crespectively represent light-extraction means swath widths of 60°, 85°,and 120°. Each one of the points making up the curves on the plotcorresponds to a specific pattern of light-extraction means (and mirrortilt angle) for a 610 mm long, round luminaire. The luminaires have 19mm diameters, and the intensity distribution of the source is shown inFIG. 14B above.

There are several points that can be inferred from FIG. 15B. Oneimportant point is that efficiency tends to increase with swath widthover the range of three swaths shown. Additionally, the data show thatfor this type of luminaires there is more advantage in tilting the endmirror when the swath width is smaller. For instance, for the 60° swathwidth case, a change in alpha tilt angle from 0° to +/−20° results inabout (“˜”) 10% more source flux exiting the luminaire. Another point toobserve is that the low point in the efficiency does not occur at alphatilt angle=0°, and in fact small positive alpha tilts result in loss ofefficiency. A final point is that the efficiencies with a large tiltangle all approach 90%. If a longer luminaire (or smaller radius) isused, this efficiency can be increased to over 90%.

As stated above, each point on the curves shown in FIG. 15B represent adifferent luminaire design. FIG. 15C shows the design cases for alphamirror tilt angle=−15°. Curves 138 a, 138 b and 138 c are profiles ofefficiency of light-extraction means along the length (shown in inches)on the luminaire surface for the 60°, 85°, and 120° swath-width cases,respectively. These curves are shaped similar to each other, and it canbe seen that higher overall efficiencies of light-extraction means arerequired for lower swath widths.

In some embodiments of the inventive luminaires a reflector can be usedfor enhancing the directionality of the light extracted from theluminaire. FIG. 16B shows a reflector which provides higher efficiencythan the reflector in FIG. 16A.

FIG. 16A shows a luminaire 140 with light-extraction means 142. FIG. 16Bsimilarly shows a luminaire 144 with light-extraction means 146. FIG.16A shows an undesired reflector 148, which is specular and concentricwith the light pipe. For illustration purposes, the reflector is shownwith a gap between the light pipe and the reflector. As shown by raytracings 152, the specular nature of reflector 142 increases the chancesof light rays exiting vertically upwards from the light-extraction meansgoing back through the light-scattering means or through the remainderof the luminaire. If light travels back through the light-scatteringmeans, a portion of it is lost, reducing illumination efficiency.

In FIG. 16B, a desired reflector 150 is used. Reflector 150 has anon-specular, diffuse reflecting surface and the reflector is shiftedaway from the light pipe. Such a surface and geometry decreases thechances that light will reflect from the reflector but not pass backthrough the light-extraction means or through the remainder of theluminaire. Specular reflectors with shapes designed to minimize the fluxrestriking the light pipe can also be used efficiently.

In FIG. 16B, luminaire 144 could be inverted so that light-extractionmeans is on the underside of the luminaire. In such an arrangement, thereflector can be shaped to impart directionality to the resulting lightbeam.

FIG. 17 shows a preferred textured pattern for light-extraction means.Such pattern could be formed from depressions on the surface of aluminaire or bumps on such surface, or both. Other patterns can also beused to achieve desired extraction efficiency. For example, hexagonalpatterns using hemispherical depressions can be used to maximize thedensity of the extractors.

FIG. 18 shows three hemispherical depressions 164 in the surface of aluminaire 166. Many such hemispherical depressions can create alight-extraction means on the luminaire. Other shapes for depressions,as shown in FIGS. 19A-19D, respectively comprise a prism, a pyramid, acone or a cylinder.

Alternatively, the hemispherical shapes 164 in FIG. 18 and the othershapes of FIGS. 19A-19D can be inverted vertically and form bumps on thesurface of luminaire 166 of FIG. 18.

FIG. 20 shows a luminaire 180 having two types of light-extractionmeans. First, a roughened surface 182, which may be formed by chemicaletching, helps to extract light from the luminaire. This is shown bylight rays 184 which intercept roughened surface 182, and are directedupwardly. Second, light-extraction particles 186 in a layer of paint 188then serve to direct light downwardly

If desired, roughened surface 182 may be used alone; that is, withoutalso including paint layer 188.

Light-Scattering Means

A preferred light-scattering means (e.g., 30, FIG. 2A) comprises a layerof paint exhibiting Lambertian-scattering and having a binder with arefractive index about the same as, or greater than that of, the core.Suitable light-scattering particles are added to the paint, such astitanium dioxide or many other materials as will be apparent to those ofordinary skill in the art. Preferably, the paint is an organicsolvent-based paint.

Three paints that have performed well are as follows: (1) An oil-basedpaint with an alkyd binder, sold by Flamuco GmbH, Munich, Germany, underthe brandname CUSTODIN, with Art. No. 52029 performed well. Theforegoing company has apparently been acquired Brillux GmbH & Co. KG ofMunster, Germany. The paint solids contain approximately 41 percent byweight titanium dioxide particles, which serve as light-scatteringparticles, and approximately 59 percent by weight alkyd binder. (2) Asecond oil-based paint sold by Nazdar of Shawnee, Kansas, as “9775 SuperOpaque White” from the 9700 series of “All Purpose Screen Ink”, alsoperformed well. (3) A third oil-based paint supplied by Sherwin Williamsof Cleveland, Ohio, as aerosol paint with TiO₂ pigment, also performedwell.

Light-scattering means of the foregoing type of paint can be applied toa luminaire by first applying a stencil to the luminaire. The stencilhas cut-out portions corresponding to the desired pattern oflight-scattering moans (e.g., 132, FIG. 15A). Then, paint is applied tothe exposed areas of the luminaire, and the stencil removed.

An alternative way to apply light-scattering means to a luminaire is toapply vinyl sticker material in the desired shape of light-scatteringmeans to the luminaire. Appropriate vinyl stickers have been supplied byAvery Graphics, a division of Avery Dennison of Pasadena, California.The film is an adhesive white vinyl film of 0.146 mm, typically used forbacklit signs.

Other Considerations

Another benefit of an aspect of the invention concerns the ability totailor the light-extraction means to accommodate the different angulardistributions of light from different light sources and still providethe same target illuminance. Referring back to FIG. 1, for instance,light source 12 may comprise a Light Emitting Diode (LED), a metalhalide lamp, a halogen lamp, or other light sources with sufficientlyhigh luminance to efficiently couple the light into the light pipe.

FIG. 21 shows a light source 12 b, which may replace light source 12 ofFIG. 1, by way of example. Light source 12 b comprises multiple lightsources, such as red, green and blue LEDs coupled into a singleluminaire. LEDs 192 a, 192 b, 192 c, and 192 d form an array ofdifferent colors such as, respectively, red, green, green and blue.Light from each of the foregoing LEDs is combined by a coupler 194 toproduce a combined output 196. The foregoing arrangement is preferablyembodied as shown in FIGS. 22A and 22B.

FIG. 22A shows a coupler 198 and an array of LEDs 200. FIG. 22B shows anend view of coupler 198, with array 200 of FIG. 22A shown as separatecomponent LEDs 200 a, 200 b, 200 c, and 200 d. Coupler 198 preferably isformed according to the principles of non-imaging optics. Coupler 198preferably has the requisite shape for performing a so-calledarea-to-angle conversion, so that the angles of light propagating fromthe LEDs at a coupler inlet 198 a, along the main optical axis of thecoupler, become reduced at outlet 198 b of the coupler. Coupler 198 maycomprise a variant of a compound parabolic concentration, which usesspecific, compound parabolic curves. Notably, inlet 198 a of the coupleris substantially rectangular (e.g., rectangular or square), and outlet198 b is substantially round (e.g., round).

Concerning coupler 198 of FIGS. 22A and 22B, even if the angulardistribution of light exiting the coupler shows color versus anglevariations, a “luminaire” (as used herein) can provide an outputdistribution that is the average of the contribution from all thecolored LEDs. This occurs because the light-extraction means scatter thelight in the length direction and produce a smeared image of the paintpattern in a direction perpendicular to the luminaire. The non-imagingarrangements of FIGS. 22A and 22B result in color variations from thesource being averaged to produce a beam pattern with very little colorvariation. If desired, a short length of light pipe lackinglight-extraction means and preceding a luminaire can further ensurebetter mixing of colors.

The principles of color mixing mentioned in the foregoing paragraph alsoapply to lamps other than LEDs, such as metal halide lamps.

Another aspect of the invention concerns the adjustability of thelight-extraction means described above to accommodate the angulardistributions of light from each one of the light sources of a metalhalide lamp, an LED lamp, or a halogen lamp, one at a time. Inparticular, the density of light-extraction means along the length of alight pipe (a secondary aspect of the present invention) can be adjustedto accommodate a metal halide lamp. Or, it can be adjusted toaccommodate an LED lamp. Or, it can be adjusted to accommodate a halogenlamp. This feature of the invention beneficially allows a designer of alighting arrangement to merely adjust the lengthwise density of thelight-extraction means to accommodate different lamps, such asmentioned. For example, a light source with a higher angulardistribution would typically use a larger change in extraction densityalong the light pipe length than one with a lower angular distribution.

More generally, the foregoing feature of the invention allows thelight-extraction means to be adjusted to accommodate the angulardistribution of light from a high illuminance light source. By highilluminance light source is meant a light source with luminance greaterthan 100,000 Nit, and more preferably with luminance greater than1,000,000 Nit. Typically, high illuminance light sources presentlyinclude HID lamps, halogen lamps, and LEDs. Other high illuminance lightsources may be devised and used in future.

Finally, the foregoing adjustability feature can be put into effect byfabricating a luminaire with a design for accommodating a desiredangular distribution of light, or the adjustment can take place afterfabrication. For instance, adhesive stickers carrying light-extractionmeans can be added or removed by an installer of a luminaire.

While the invention has been described with respect to specificembodiments by way of illustration, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true scope and spirit of the invention.

1. A luminaire with directional side-light extraction, comprising: a) alight pipe with a light-carrying core; the light-pipe having a first endin which light from a light source is received, a second end, and alongitudinal axis; b) light-extraction means on the surface of the coreof the light pipe, along a first longitudinal side of the luminaire; thelight-extraction means being confined to a radial swath of theluminaires along the longitudinal axis of the luminaire, ofsubstantially less than 180°; c) angles passing through a first planeintersecting a radial center of the light-extraction means being termedalpha angles or alpha component angles; and angles passing through asecond plane orthogonal to the first plane being termed beta angles orbeta component angles; with alpha angles being referenced to the secondplane and beta bangles being referenced to the first plane; d)light-saving means on the second end for directing saved light from thesecond end towards the first end, at redirection angles other than anexcluded range of redirection angles, so long as the photon content oflight at alpha redirection angles is at least 10 percent of the photoncontent of light at beta redirection angles, where the excluded range ofredirection angles is defined by:|β_(r)|<=20° and |α_(r)|<|β_(r)|/10, where β_(r) is the beta redirectionangle and α_(r) is the alpha redirection angle; and e) thelight-extraction means being adjustable to accommodate angulardistributions of light from each one of the light sources of a metalhalide lamp, an LED lamp or a halogen lamp, one at a time.
 2. Aluminaire with directional side-light extraction, comprising: a) a lightpipe with a light-carrying core; the light-pipe having a first end inwhich light from a light source is received, a second end, and alongitudinal axis; b) light-extraction means on the surface of the coreof the light pipe, along a first longitudinal side of the luminaire; thelight-extraction means being confined to a radial swath of theluminaire, along the longitudinal axis of the luminaire, ofsubstantially less than 180°; c) angles passing through a first planeintersecting a radial center of the light-extraction means being termedalpha angles or alpha component angles; and angles passing through asecond plane orthogonal to the first plane being termed beta angles orbeta component angles; with alpha angles being referenced to the secondplane and beta bangles being referenced to the first plane; d)light-saving means on the second end for directing saved light from thesecond end towards the first end, at redirection angles other than anexcluded range of redirection angles, so long as the photon content oflight at alpha redirection angles is at least 10 percent of the photoncontent of light at beta redirection angles, where the excluded range ofredirection angles is defined by:|β_(r)|<=20° and |α_(r)|<|β_(r)|/10, where β_(r) is the beta redirectionangle and α_(r) is the alpha redirection angle; and e) thelight-extraction means being adjustable to accommodate angulardistribution of light from a high illuminance light source withluminance greater than 100,000 Nit.
 3. The luminaire of claim 2, whereinthe light-extraction means is adjustable to accommodate the angulardistribution of light from a high illuminance light source withluminance greater than 1,000,000 Nit.
 4. A luminaire with directionalside-light extraction, comprising: a) a light pipe with a light-carryingcore; the light-pipe having a first end in which light from a lightsource is received, a second end, and a longitudinal axis; b)light-extraction means on the surface of the core of the light pipe,along a first longitudinal side of the luminaire; the light-extractionmeans being confined to a radial swath of the luminaires along thelongitudinal axis of the luminaires of substantially less than 180°; c)angles passing through a first plane intersecting a radial center of thelight-extraction means being termed alpha angles or alpha componentangles; and angles passing through a second plane orthogonal to thefirst plane being termed beta angles or beta component angles; withalpha angles being referenced to the second plane and beta bangles beingreferenced to the first plane; d) light-saving means on the second endfor directing saved light from the second end towards the first end, atredirection angles other than an excluded range of redirection angles,so long as the photon content of light at alpha redirection angles is atleast 10 percent of the photon content of light at beta redirectionangles, where the excluded range of redirection angles is defined by:|β_(r)|<=20° and |α_(r)|<|β_(r)|/10, where β_(r) is the beta redirectionangle and α_(r) is the alpha redirection angle; and e) thelight-extraction means being adjustable to accommodate angulardistributions of light from an array of LED lamps having differentcolors.
 5. The luminaire of claims 1, 2 or 4, wherein the radial swathfor the luminaire is between 20 and 60°.
 6. The luminaire of claims 1, 2or 4, wherein the radial swath for the luminaire is from 60 to 130°. 7.The luminaire of claims 1, 2 or 4, wherein the second end of theluminaire has a mirror for reflecting back into the luminaire lightreceived by the mirror.
 8. The luminaire of claims 1, 2 or 4, whereinthe light-extraction efficiency of the light-extraction means of theluminaire increases non-monotonically from the first end to the secondend of the light pipe.
 9. The luminaire of claims 1, 2 or 4, wherein theilluminance over each of each sequential 5 percent length of theluminaire is uniform to within 10 percent of the average illuminancealong the length of the luminaire.
 10. The luminaire of claims 1, 2 or4, wherein the luminaire further comprises: a) an elongated reflectorshaped to partially surround the luminaire and having a longitudinalopening facing the first longitudinal side of the luminaire; thereflector serving to reflect light scattered by the light-extractionmeans to a desired target area to be illuminated; b) the reflectorhaving a non-specular, diffuse reflecting surface; and c) the width ofthe reflector at the opening to the reflector being at least 1.3 timesthe maximum cross-sectional dimension of the luminaire.
 11. Theluminaire of claims 1, 2 or 4, wherein the light-extraction means of theluminaire further comprises a textured surface of the light pipe core.12. The luminaire of claims 1, 2 or 4 in combination with a freezer caseand the light source, wherein the luminaire is placed inside of thefreezer case and the light source is placed outside of the freezer case.